To date, no model appears to exist which relates the performance of the intact left ventricle to the behavior of individual muscle fibers. Other investigators have proposed simplified models which contain only circumferential muscle fibers which contract and relax, synchronously, exhibiting the same tension, shortening and velocity of shortening. The model which is under investigation in this study will relate experimentally determined pressure-dimensional data to the contractions of local portions of the ventricular wall. Initial steps in the development of an axisymmetric finite element model for the left ventricle have been developed. This model is based on observed ventricular geometry and fiber elasticity. However, the model is presently applicable only to the end diastolic ventricle. The general intent of this study is to extend the applicability of the model to the ventricle during the entire cardiac cycle. The ultimate objective is then to use this model to evaluate the heterogeneous, mechanical response of normal, hypertrophied and infarcted left ventricles. The major indices of mechanical response are fiber stress, fiber strain, fiber strain rate and internal energy. These quantities will be used to characterize myocardial function in terms of contractility and end diastolic fiber length.